Vacuum-pump



(No Model.)

I'. H. SMITH.

VACUUM PUMP. No. 321,764. Patented July 7, .1885.

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UNITED STATES PATENT OFFICE.

FREDERICK H. SMITH, OF BALTIMORE, MARYLAND.

VACUUM-,PUM P.

SPECIFICATION forming part of Letters Patent No, 321,764, dated July 7, 1885.

Application tiled May 2l, 1884.

(No model.)

To all whom it may concern:

Be it known that I, FREDERICK I-I. SMITH, a citizen of the United States, residing at Baltimore city, State of Maryland, have inventedl P and P are pump-chambers, whose lower ends are fitted into or otherwise connected with the opposite ends of the long flexible tube F. The middle portion of this flexible tube passes over the pulley-wheel IV, and each end of the exible tube contains a quantity of mercury, as indicated bythe dotted lines within the tube, and a small hole, H,'at the middle of the length of the tube maintains connection between the outer air and the air within the tube, while it also facilitates the placing or removing of the mercury.

V and V are vacuum-tubes having their upper ends shaped to receive the stems of the dotted lamp-globes L L or other objects to be exhausted, and the lower ends of these vacuum-tubes pass down through the roofs of the pump-chambers and extend down through the interiors thereof nearly to their floors.

O and O are outlet-valves having guidingstems, which project down into the pumpchambers through apertures in the roofs thereof, and I and I are inlet-valves having guiding-stems which proj ect upward into the lower ends of the vacuum-tubes.

The operation of my improved vacuumpump is effected by drawing the middle part of the exible tube back and forth over the pulley-wheel, thereby causing the mercury to ascend and descend alternately within the pump-chambers. As the mercury descends below the floor of the pump-chamber, (shown in the right-hand side of the drawing,) the outlet-valve floats downward against and closes the aperture in the -roof of the pump-chamber, and the inlet-valves next float downward from and open the lower ends of the vacuum= tubes, thus allowing the air within the vacuum-tubes and their connections to expand and fill the empty space in the pump-chamber. As the mercury ascends again to the roof of the pump-chamber, as shown in the left-hand side of the drawing, the inlet-valves iioat upward against and close the lower ends of the vacuum-tubes, and the outlet-valve next iioats upward from the roof of the pump-chamber andv opens the aperture therein, thus allowing the air imprisoned within the pump-cha1n ber to escape into the outer atmosphere. This alternating descent and ascent of mercury within the pump-chamber is continued until, by the removal of successive portions of air from the vacuum-tubes and their connecting lamp-globes or other objects, the desired de gree of rarefaction is reached.

The progress of rarefaction can be determined by attaching a pressure or spark gage to any part of vthe vacuum-tubes, or to the objects to be exhausted, or small eye-pieces of glass can be inserted at such points in the iiexible tube as will show when the mercury column stands at thirty inches. Bulbs containing moisture-absorbents can also be at tached to the vacuum-tubes or objects to be exhausted. The upper ends of the vacuumtubes are shown in the drawing as being bellmouthed to receive stopperseals pierced by the stems of the lamp globes; but these upper ends of the vacuum-tubes may be shaped in many other convenient ways to accommodate different objects. The motion of the flexible tube over the pulley-wheel may be produced by merely drawing it back and forth by hand; or the motion may be rst applied to the wheel by belt or crank or otherwise, and the revolution of the wheel moves the iiexible tube. This flexible tube may be all in one piece, as shown in the drawing; or it may be in two pieces connected over the wheel with each other by means of a chain or belt or cord, and the wheel may be either fixed in one place or adjustable vertically or horizontally, to com pensate for any distortion of the iiexible tube. I do not, however, confine myself to this particular method of raising or lowering the mercury in the pump-chamber, as this maybe effected in many ways, new and old, and I may hereafter wish to use in` connection with this improved mercury vacuum-pump the improved method of moving the mercury which I have embodied in another application now on le.

The form of valve shown in the drawing is that which places fiat surfaces in contact with fiat surfaces, and the overflow of mercury completes the hermetic seal; but these valves may be in many other suitable shapes.

The outlet-valve ispreferably made of heavy material, so as to close down promptly and thus leave a full bed of mercury overiiowing the roof of the pump-chamber, while the inlet-valves are of lighter materials, so as to iioat upon the iirst rise of the mercury and close the vacuum-tubes at once.

The drawing shows a double pum p, or, rather, two pumps, connected to one ilexible tube, as this best utilizes the motion of the tube in both directions; but single pumps are the best for noncommercial uses.

The roof of thepump-chamber is preferably of wood resting on a shell", as shown, as this form facilitates removal if access to the interior is desired, and the overilow of mercury renders the joints all air-tight.

By passing the vacuum-tubes of my improved pump directly downward through the roof of the pump chamber to their valveseats in the interior thereof, I avoid the use of the long, slender, crooked, and fragile glass tubes which are necessarily used in those pumps in which the vacuum-tubes open into the pump-chamber through its sides or bottom. I thus avoid all liability to breakage or obstruction in these tubes, and so simplify and render accessible all parts of the apparatus that this pump can be made of much larger sizes than any other, and it can be operated much more rapidly, as it offers no crooked channels or other impediment to the rapid ebb and ilow of the mercury, and its valves are free and frictionless.

I claim- A vacuum -pump consisting of a pumpchamber open at its bottom, and provided with a valved roof, a vacuum tube or tubes extending down through the said roof and having valves at their bottoms, and mechanism, substantially as shown, for exhausting the air from said chamber and tubes, as and for the purpose set forth.

FREDERICK H. SMITH.

lftiiesses:

XV. 3.XV1L1i1NsoN, JAMns E. WILkINsoN. 

